It has always been a goal of aircraft designers to improve the steering and maneuvering capability of aircraft. Improving steering and maneuvering is especially important for small supersonic aircraft. This is because they often have special requirements related to their ability to "track" or "aim" their fuselage in a particular desired direction. Associated with this is a further requirement to change "tracking" or "aiming" direction quickly.
A problem with such aircraft is that when flying at supersonic speeds, their fuselage experiences an aft shift of its aerodynamic center. Such a shift causes the aircraft to have a highly static stabilization in the longitudinal direction which adversely affects the maneuverability of the aircraft. To solve this problem, designers have developed canards, attached to external portions of the fuselage, for controlling the location of the aerodynamic center. Although canards are effective for this purpose, their use has created another problem; that is, they significantly contribute to the drag and observables of the aircraft. Therefore, an object of the present invention is to provide improved canards that increase the steering and maneuvering capability of an aircraft, and at the same time minimize the drag and observables.
The following U.S. patents disclose various past methods of employing canards and other external control surfaces: U.S. Pat. No. 3,152,775, granted to Boyd; U.S. Pat. No. 3,642,234, granted to Kamber et al; U.S. Pat. No. 3,680,816, granted to Mello; U.S. Pat. No. 3,730,458, granted to Haberkorn; U.S. Pat. No. 3,881,671, granted to Bouchnik; U.S. Pat. No. 3,883,094, granted to Mederer; U.S. Pat. No. 4,247,062, granted to Brueckner; U.S. Pat. No. 4,336,914, granted to Thomson; U.S. Pat. No. 4,354,646, granted to Raymer; U.S. Pat. No. 4,357,777, granted to Kulik.
Particularly pertinent to the present invention is Haberkorn, U.S. Pat. No. 3,730,458, and Mederer, U.S. Pat. No. 3,883,094. Haberkorn relates to a jet-controlled aircraft that has trim and control fins. The fins unfold from a position flush against the fuselage to a position extending laterally therefrom, with the fins further having the capability of holding any position inbetween. In addition, when the fins are in the laterally extending position, they have the ability to pivot about a "Y" axis which is perpendicular to the longitudinal axis of the aircraft.
In a manner similar to the present invention, Haberkorn discloses a pair of fins or canards which are rotatable about said "Y" axis. However, a disadvantage to Haberkorn is that no provision is made for any such rotation of the canards when in intermediate positions between the folded and lateral positions. In conjunction with this, another disadvantage is that one canard does not have the capability to rotate independently from the other. A further disadvantage to Haberkorn is that the canards do not have the capability to move from a fully folded position against the fuselage to a downwardly extending position relative to the fuselage.
Mederer discloses a foldable canard assembly that includes a pair of canards folded together as a single canard extending vertically downward from the fuselage. The canards unfold to a position extending laterally from the bottom of the fuselage, but cannot fold into a retracted position against the fuselage.
A disadvantage to this assembly is that the canards have only one degree of freedom for pivotal movement. They cannot pivot rotationally when in the downward vertically extending position, and further, they cannot rotate when the canards are in the lateral position, or any position in between. Another disadvantage to the Mederer assembly is that since the canards cannot retract against the fuselage, they increase the drag and observables of the aircraft.
The above-mentioned disadvantages, and the advantages of the present invention, will become apparent upon further reading of this application.